Type head driving and stopping apparatus



United States Patent lnventors Herbert Behrens Neuenburg; Hans Elsner, Bremen-Gartenstdt Vahr, Germany Appl. No. 778,241 Filed Nov. 22, 1968 Patented Dec. 22, 1970 Assignee Olympia Werke AG Wllhelmshaven, Germany TYPE HEAD DRIVING AND STOPPING APPARATUS 17 Claims, 9 Drawing Figs.

11.5. C1. 197/18, l78/34:197/52.197/55 Int. Cl. B4lj 23/10, B41j 1/60 Field ofSearch 197/16, 18, 52, 55; 178/34 [56} References Cited UNlTED STATES PATENTS 299,754 6/1884 Dodson 197/ 1 8 1,598,028 8/1926 Tyberg 197/16 2,900,848 8/1959 Henn-Collins 74/768 3,014,569 12/1961 Palmer 197/16 3,144,820 8/1964 Wales, Jr. 101/91 3,205,305 9/1965 Clark et a1. 178/34 Primary Examiner-Robert E. Pulfrey Assistant Examiner-Clifford D. Crowder Attorney-Michael S. Striker ABSTRACT: A rotary type-head is driven by means of a planetary transmission which has a normal condition in which the type-head is continuously rotated, and a stop control condition in which the type-head is turned by a coupling means moving along a cycloid path under the control of planetary gear means of the transmission, so that the type-head is stopped at the reversing point of the cycloid path in a position for printing a typeface selected by actuation of the corresponding key.

PATENTED DEC22 I970 SHEET 2 OF 6 INVENTOR lien an r 867m aw s ATTORN EY PATENTEU 05022 I978 SHEET 6 BF 6 INVENTOR lit-wear Renews Qiwiiiiii z By M vs E4 5 Ala/g 0771; /de/ f aw} ATTORNEY TYPE HEAD DRIVING AND STOPPING APPARATUS BACKGROUND OF THE INVENTION The present invention relates to typewriters provided with a rotary type head having one or several circular rows of 5 typefaces, and being stopped in a selected position for printing a selected typeface when a key is actuated.

The U.S. Pat. No. 1,598,028 discloses a type head drive in which the type head is slowed down before stopping in a selected position, which is accomplished by superimposing an opposite motion on the normal rotary motion of the type head The control of the type head is not efiected by positive engagement of mechanical parts.

It is one object of the invention to provide a type head driving and stopping apparatus in which the type head is stopped by the positive mechanical engagement of parts.

The U.S. Pat. No. 3,205,305 discloses a planetary transmission controlling the stopping of the type head. Each type moves along a hypocycloid path in relation to the outer periphery of the type head, and a reversing point of the path can be used for printing the respective type. Since a certain time is required for the printing operation during which the type is pressed against the writing surface, the type performs a rolling motion on the copy sheet, together with the adjacent types which tend to produce undesired imprints in addition to the imprint of the selected type and character. The spacing between the types of each row must be greater than when printing is carried out with a stopped type head.

It is another object of the invention to overcome this disadvantage of known type head driving arrangement, and to provide a type head driving and stopping apparatus in which the selected type does not perform a rolling motion during the printing operation.

SUMMARY OF THE INVENTION With the above objects in view, the present invention relates to a type head driving and stopping apparatus which controls a type head rotatable about a main axis and having at least one circular row of typefaces successively passing through a position of readiness located opposite a printing area during rotation of the type head in a normal position spaced from the printing area. The type head means is movable to a printing position in which the respective typeface exerts pressure on the printing area.

In accordance with the invention, differential transmission means connect drive means with the type head means and include planetary transmission means having at least one planetary axis spaced from the main axis. Control means are provided for shifting the differential transmission means between a normal condition in which the planetary means revolves about the main axis without rotating, and a stop control position in which the planetary means revolves about the main axis and also rotates about the planetary axis.

Coupling means connect the planetary means with a type head means and include a coupling member secured to the planetary means radially spaced from the planetary axis.

As a result, the type head means is rotated at a constant rotary speed in the normal condition of the differential transmission means to successively place the typefaces opposite the printing area, whereas in the stop control condition the coupling member, moving along a cycloid or cardioid path having a reversing point, rotates the type head means at a cyclically varying speed and at a minimum speed at the reversing point of the cycloid path.

Selector means preferably including keys and a selector circuit, are provided for selecting one of the typefaces for printing. The control means are actuated by the selector means to shift the differential transmission means to the stop control position when the selected typeface is spaced a predetermined angle, for example 180, from the position of readiness located opposite the printing area. Actuating means are operated by the differential transmission means to move the type head means from the normal position to the printing position when the type-head means at least substantially stops at the reversing point of the cycloid path of the coupling member, and the selected typeface is in the position of readiness opposite the printing area.

In the preferred embodiment of the invention, the planetary means include a pair of first diametrically disposed planetary gears meshing with a sun gear secured to the main shaft of the transmission. In the normal condition of the transmission, the sun gear rotates at the same speed as the drive gear, and the planetary gears, with coupling members thereon, rotate at the same speed as the drive gear on which they are mounted whereby the planetary gears with the coupling members revolve about the main axis at the same speed as the drive gear. In the stop control condition of the differential transmission means, the control means stop the sun gear so that the planetary gears roll on the sun gear while revolving about the main axis. Consequently, the coupling members move about cardioidal paths having reversing points. A double-armed fork means has a pair of diametrically guideways in which the coupling members are located, and is connected to the type head shaft for rotation, and is tilted with the carrier of the type head means.

The differential transmission means include a second planetary transmission including a stop wheel on the main shaft which can be stopped by stop levers under the control of stop magnets so that the main shaft of the transmission carrying the first sun gear can be stopped in the stop control condition of the transmission. A part of the second planetary transmission is stopped in the normal condition of the transmission so that the sun gear rotates at the same speed as the drive gear on which the journals of the planetary gears are mounted.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a vertical sectional view illustrating an embodiment of the invention;

FIG. 2 is an exploded perspective view illustrating the apparatus;

FIG. 3 is a diagrammatic view schematically illustrating the apparatus and the meshing relationship between the elements of the differential transmission means;

FIG. 3a is an elevation, partially in section, illustrating a modified apparatus of the invention;

FIG. 4 is a schematic plan view illustrating the cardioidal paths of the planetary gears and the actuating means for tilting the type head to the printing position;

FIG. 5 is a cross-sectional view taken on line V-V in FIG. 1 and illustrating parts of the selector circuit of the apparatus;

FIG. 6 is a fragmentary perspective view illustrating typewriter selector keys and parts of the coding selector circuit controlled by the same;

FIG. 7 is a diagram illustrating the coded selector circuit of the apparatus, including electronic components, stop magnets, and a locking and releasing magnet; and

FIG. 8 is a diagram illustrating a simplified coded selector circuit in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Rotary Drive As best seen in FIGS. 1, 2 and 3, a drive gear 9 is driven from a motor M by means of a motor gear 10, and rotates about a main shaft 11 which is mounted in bearings 43 supported by supporting means 44. Motor gear 10 and drive gear 9 may be connected by a gear belt instead of meshing directly.

Drive gear 9 carries journals 12 on which planetary gears 13 are mounted for rotation in a position meshing with a sun gear 14 on main shaft 11.

Planetary gears 13 carry fixed cranks 130 which have spherical or cylindrical heads 15 whose centers are located directly above the pitch circles of the teeth of gears 13. A doublearmed fork member 16 has two diametrically disposed radial guideways 16a in which heads 15 are guided. The center of fork member 16 is secured to a type head shaft 17 which is coaxial with main shaft 11. A type head 24 is connected with the upper end of type head shaft 17 for rotation therewith.

Type Head Arrangement Type Head shaft 17 is mounted in bearings 18 and 19 of a member 20 which forms part of a tiltable carrier 21 which is mounted for pivotal movement about a pivot pin 22 which is supported by a stationary frame portion so that carrier 21 can tilt between the illustrated position of rest, and a printing position in which a typeface on type head 24 abuts a platen 42 to produce an imprint. Lines are typed in axial direction of the platen, and the axis of pivot means 22 is parallel to the axis of platen 42 and to the direction of the typed lines. A spring, not shown, connects a stationary frame portion with carrier 21 to hold the same and type head 24 in the illustrated position of rest abutting a stop, not shown.

Below drive gear 9, a second drive gear 9a is mounted on main shaft 11 for free rotary movement and is driven by a second motor gear 10a. The transmission ratios between gears 9, 10 and 9a, 100 are selected so that drive gear 9 rotates at twice the rotary speed than drive gear 9a.

Drive gear 9a carries downwardly projecting journals 47 on which pairs of planetary gears 46 and 46a are mounted for rotation. The smaller planetary gears 46a mesh with a second sun gear 45 secured to main shaft 11. The larger planetary gears 46 mesh with an inner orbit gear 48d of a cam means 48. The ratios between gears 46 and 48d, and between gears 45 and 46a are the same, and preferably 1 3.

Cam means 48 is mounted on main shaft 11 for free rotary movement and has a hub formed as a cam 48a, see FIGS. 1 and 4, whose projecting cam portion 48'a cooperates with a cam follower roller 49 mounted on a transverse end portion 21a of tiltable carrier 21 for rotation. When projecting cam portion 48'a engages roller 49 during each revolution of cam means 48, carrier 21 is tilted together with type head shaft 17 about pivot means 22 so that the type 24t which confronts platen 42 is moved to a position engaging the platen 42. Double-fork member 16 tilts with carrier 21, while crank heads 15 are mounted in the frame portion 44, and in order to permit relative movement, the guideways 16a of double-fork member 16 are of sufficient axial height, and crank heads 15 are preferably spherical. A conventional locking means, not shown, may be actuated by the tilting movement of carrier 21 to lock type head 24 so that the same cannot turn out of the position in which a selected type head 24: is located in the operative position confronting platen 42.

Cam means 48 includes a disc-shaped locking part 48b between hub cam 48a and the flanged portion which has the inner gear 48d. Locking part 48b has a locking cutout 48c cooperating with a locking pawl 50 mounted for pivotal movement on a pivot pin 57 supported by a frame portion 55. Locking pawl 50 has a bifurcated arm 500 which embraces a portion of the armature 56a of an electromagnet 56 which, when energized, attracts armature 56a against the action of spring 53 so that locking pawl 50 is withdrawn from locking recess 48d.

Locking pawl 50 operates the two movable switch arms 52 and 52, of a switch 52, shown in FIG. 7. When locking pawl 50 is in the normal position of rest locking cam means 48, switch arms 52 and 52, interrupt two circuits shown in FIG. 7, which are closed when electromagnet 56 is energized and locking pawl 50 withdrawn from locking cutout 48c.

Control of the Type Head When rotation of cam means 48 is blocked by locking pawl 50, rotation of drive gear 9a is transmitted by journals 47 to planetary gears 46 which roll on the inner orbit gear 48d whereby planetary gears 46 turn and drive sun gear 45 with main shaft 11 which rotates in the same direction of rotation as drive gear 9a, but twice as fast and at the same rotary speed as drive gear 9. Sun gear 14 rotates at the same speed as drive gear 9 and in the same direction of rotation. Planetary gears 13 do not roll on sun gear 14, so that members 130, 15 and 16a, 16 constitute coupling means by which the motion of main shaft 11 is transmitted to the type head shaft 17 which rotates at the same rotary speed and in the same direction of rotation as main shaft 11 and drive gear 9. A stop wheel 54 with eight ratchet teeth A to H is disposed below support frame wall 44 and secured to main shaft 11, as shown in FIGS. 2, 3, 5, and 7.

Type head head 24 is provided with four annular rows of typefaces 24:, each of the annular rows having 24 typefaces so that four typefaces are disposed in a column on type head 24. Consequently, it is necessary to stop the type head 24 in a selected one of 24 different angular positions, in each of which a column of four typefaces 24: is located opposite platen 42. In accordance with the invention, the stopping of the rotary movement of the type head is to take place gradually and without a strong impact of the type head on the means by which it is stopped in a selected angular position.

In the lower supporting frame portion 55, three stop levers 66 are mounted spaced from each other in circumferential direction which are respectively connected with the armatures 67a of three electromagnets M 1, M 2, M 3 which are biased by springs 67 to turn stop levers 66 to a position retracted from the teeth of stop wheel 54. When one of the stop magnets M l, M 2, M 3 is energized, the armature 67a is attracted against the action of spring 67, and the respective stop lever 66 is turned to a stop position located in the path of movement of a tooth of stop wheel 54.

As shown in FIG. 8, locking magnet 56 is connected in series with stop magnets M 1, M 2, M 3, and shunted by capacitor 88. Whenever one of the stop magnets M l, M 2, M 3 is energized to actuate stop means 66, 54 to stop main shaft 11, locking magnet 56 is also energized to operate locking pawl 50 to release locking part 48b of cam means 48. This is schematically illustrated in FIG. 3 by a combined stop and release means 66', 50.

Each of stop levers 66 can cooperate with each of the eight teeth A to H of stop wheel 54, resulting in 24 angular stop positions of stop wheel 54 and of the main shaft 11. FIG. 5 shows the possible position, and illustrates only stop wheel 54 with teeth A to H, main shaft 11, and stop magnets M 1, M 2, M 3 with the associated stop levers 66, the stop magnets and stop levers 66 being only schematically indicated. Due to the fact that teeth A to 1-1 are spaced 45, and stop magnets M l, M 2, M 3 with stop levers 66 are spaced ,the eight different angular positions in which each stop lever stops stop wheel 54 with main shaft 1 1, are staggered to the positions in which the main shaft is stopped by the respective other stop levers 66.

The following table indicates the 24 positions of stop wheel 54 in which teeth A to H are stopped by stop lever 66 under the control of the stop magnets M l, M 2, M 3.

POSIUOn 1 2 3 4 5 6 7 8 9 10 n 12 Tooth A D G B E H 0 F A D G MagnetM I. 2 '3 1 2 3 1 2 3 1 2 3 Position 13 14 15 16 17 1s 19 21 22 23 24 To0th EHCFA BEHCF MagnetM I 2 3 I Z 3 l 2 3 l 2 3 stop wheel with three teeth and cooperating with eight stop levers and stop magnets, or to provide the stop wheel with four teeth cooperating with six stop levers and magnets, or six teeth of the stop wheel may cooperate with four stop levers and stop magnets. The shorter the time-of response of the stop magnets and stop levers is, the smaller can be-the angular spacing of the teeth of the stop wheel.

Operation 7 a It is assumed that the above-described type head drive is fix edly-mounted in the machine frame, and that a paper carriage, not shown, supports platen 42, and is movable in a'writing direction, and also in an'opposite returndirection relative to typehead24r,

When by energization of a selected stop magnet M -l, M 2, or M 3, stop wheel 54 is stopped together 'with main shaft 11 and sun gears 45 and 14, drive gear 9 continues to rotate 'so that planetary gears 13 roll on'sun gear l'4, and perform one revolution when drive gear 9 performs a one" revolution. Coupling heads. 15 rotate with planetary gears 13 about journals l2, and also revolve about the axisof mainshaft 11 and type head shaft 17 so that coupling heads 15 move along cardioid-shaped paths 15 15a, as schematically shown in FIG. 4. The movement of coupling heads 15 has 'a circumferential component in the major parts of the cardioidal paths 1 150 so that type head shaft 17 is turned by the coupling fork member 16, but at the point U of the cardioidal paths 1 a, the direction of movement of coupling heads is reversed in longitudinaldirection of the guideways 160 so that no circumferential motion is transmitted to coupling forkmember l6 andtype head shaft 17 with type head 24' is stopped. 1

FIG. 4 is a schematic plan view, showing cam means 48 in a position in which the projecting cam portion 48'a is located opposite the platen so that cam followersroller 49 engages a circular peripheral portion of the cam track of cam 48a. The dash and dot line 12a indicates the circle along which the axes of journals 12- move. Guideways l6aof coupling fork member l6are as schematically indicated.

The selection of one of the 24 typefaces 24: of type head 24 depends onthe selection of the angular positionin which drive gear 9 and main shaft 11 are stopped. a

The tilting of the typ'e'head 24 to render one of the four circular lines of typefaces24t operative, is effected in a conventional manner by a device 60 which includes an electomagnet 600, as shown in FIG. 1. For the purposes of the present invention, it may be assumed that only one circular line of typefaces 24: is provided on type head 24. v a V The angular printing movementof tiltable carrier 21 with type head 24 about pivot 22 takes place automatically when locking recess 48c is released by locking and releasing magnet ,56.

When locking and releasing magnet 56 is energized together with one of the stop magnets M l, M 2, M 3, locking pawl 50 is retracted from locking cutout 48c and engages the circular periphery of locking'part 48b. Magnet 56 has a delayed deenergization so that locking pawl 50 cannot'fall again into cutout 48c before cam means 48 has started to rotate.

One of teeth A to H of stop wheel 54 is selected in a manner I which will be described hereinafter, and runs against the respective selected stop lever 66 so that main shaft 11 is same direction of rotation as drive gear 9 and at the same rotary speed for one revolution. I

Cam follower roller 49 of the tilta ble carrier 21 rolls along the cam track of cam 48a of cam means48 and when it passes over the projecting cam portion 48'a, carrier 21 is tilted together with type head 24 to a position in which the respective typeface 24! of type head 24 abuts platen 42, or an inked ribbon between type head 24 and platen 42. This tilting printing motion takes place at the moment in which type head 24 does not rotate due to the fact that earn 480 has turned half a revolution out of the position illustrated in FIG. 4 so that coupling heads 15 are at the points U of the cardioid paths 15a as shown in dash and dot lines in FIG; 4.

It is not necessary that the locked position of rest of cam means 48 is spaced 180 from the position in which carrier 2! is tilted and coupling heads 15 arelloc'ated at the reversing points of the cardioid-shapedpaths. The position of rest may be more closely spaced from the points U, and the angular 1 position of the projecting cam portion 48'0. of cam 48 must be and after the deenergization of the respective magnets. This longer time period has no bearingon -the typing speed which can be obtained, since it coincides with the time required for stopped in an angular position determined by the selection of a tooth A to H, and of one of the stop magnets M l, M 2, M3;

Planetary gears 464 are driven gear 9a to'roll on the stopped transmitted to the inner orbit gear of cam means 48 in a ratio of 2 l. Due to'the rotation of planetary gears 46 by planetary the selection of the next following character and type face.

' Selection of Typefaces I Assuming 24 columns of four type typefaces 24!, or four circular rows 'of 24 typefaces 24!, the type head 24 has 96 typefaces 24t. Assuming the typewriter to have 48 keys, each of which is associated with two characters and typefaces in a typewriter provided with a shift key in the usual manner, each stop magnet M 1, M 2, M 3 is controlled by 16 keys. As shown in FIGS. 6 and 8, a coding arrangement is provided for the selection of typefaces by keyoperations.

Keys K have key stems 69 guided in a guide member 102 and beingprovided with projections 69a,. 69b and 691 at different points. Projections 69a and 69b cooperate with groups gized to select one of the circular-rows of typefaces 24: for

printing by tilting type head 24 in a mannerwhich is not an object of the present invention.

- As shown in FIGS. 5 and 7, eight radial contact springs 68a to 6811 are mounted on the bottom face of stop wheel 54 insulated from each other, which are all in sliding contact with an outer contact track 74 which is'divided into three segments 74,, 74,, 74,. The inner ends of contactsprings 68a to 68!: respectively slide along inner circular contact rings 75a to 75h, the subscripts corresponding to the reference characters of the teeth of .stop wheel 54. Contact rings 75a to 75!: are I provided on a selector disc 73 which is fixed on the supporting frame portion 55. Each tooth -A toH-of stop wheel 54 is associated with one of the contact rings 75a to 75h and one of the contact springs 68a to 68!: which during the rotation of stop wheel 54, cyclically connect contact'segments 74, to 74, with contact rings 75a to 75k. Code mm; 760 to 76h, which are operated by the keys, as shown in FIG. ,6, are respectively connected by code lines 77 with contact rings75a to 75!: as shown in FIG. 7. By selection of one of the code contacts. for

gears 46a, inner orbit gear 48d and cani means 48 rotate in the 75 example codecontact 763, a corresponding tooth G of the G by means of the respective stop lever 6.

Stop magnet M 1, M 2, M 3 are connected by a line 86 includinga diode 83 and a resistor 97 to the positive terminal of a voltage source V. Locking and releasing magnet 56 is connected in series with the stop magnets M 1, M 2, M 3 over a diode 84 so that the selected stop magnet is always energized over diode 84 when locking and releasing magnet 56 is energized over a transistor 90. The source of the energizing current for magnets 56, and M l to M 3, is a capacitor 81 which is connected over a charging resistor 82 with the positive terminal. A flip-flop 91 opens the transistor 90. The control voltage for flip-flop 91 is supplied from a voltage divider 94 which is connected into the coding line 77 in series with code contacts 76a to 76h, and also to the negative terminal of the voltage source. The control voltage is interrupted by the rest contact 52 of switch 52.

The actuation of a selected stop magnet M 1, M 2, M 3 takes place when one of the contact springs 68a to 68h, for example contact spring 68g which corresponds to the code contact 76g closed by the respective control contact 71, reaches contact segment 74, during the rotation of the contact springs 68a to 68h with stop wheel 54. In this moment, a control current flows through resistor 97, diode 83, line 86, the closed control contact 71,, the winding of stop magnet M 1, the line 87,, the contact segment 74,, contact spring 683, contact ring 75 and the respective wire of line 77 to code contact 76g and "from there to the voltage divider 94 which applies through the still closed rest contact 52:, of switch 52 a control voltage to the flip-flop 91 so that the same switches. Transistor 90 is opened, and capacitor 81 discharges through the locking and releasing magnet 56, diode 84, the closed control contact 71,,

"in the present example, and from thereover the same circuit path as described above to the negative terminal so that magnets 56 and M 1 are energized and locking pawl 50 releases locking part 48b of cam means 48 while stop lever 66 of stop magnet M 1 engages tooth G of stop wheel 54 and stops the same so that the above described differential transmissions reduce the rotary speed of type head shaft 17 and bring it to a stop when the projecting cam portion 48'a engages cam follower roller 49 to cause a tilting printing motion of carrier 21 with type head 24.

Return to Position of Rest the voltage source, and whose voltage switches flip-flop 91 which is already disconnected from the voltage source by the open "break" contact 52 so that transistor 90 is closed again and capacitor 81 can be charged over its charging resistor 97 to be ready for the next operation. Locking and releasing magnet 56 is deenergized, and the spring 53 urges locking pawl 50 into the locking cutout 48c of locking part 48b of cam means 48.

In the meantime, the energized stop magnet, for example stop magnet M 1, holds the respective stop lever 66 in a position stopping the stop wheel 54 until stop pawl 50 drops shortly before the completion of one revolution of cam means 48, again into the cutout 480 of stop part 48b. The motion of stop pawl 50 releases switch 52 so that the energized stop magnet, in the present case stop magnet M 1, is also deenergized and its stop lever 66 is pulled by spring 67 out ofengagement with the respective tooth G of stop wheel 54 so that the same can start to rotate due to the fact that planetary gears 46 start to roll on the inner orbit gear 48d of the stopped and locked cam means 48. In this manner, the normal position of rest of all parts is reestablished until the next key is operated, unless the previously actuated key K with its stem 69 is held in the depressed position in which event another printing operation for printing the same character is immediately started.

It is necessary to open the control contact and code contact which were previously'closed by operation of a key, in the present example control contact 7I,'and code contact 763. This is accomplished by a conventional ball-locking device for the keyboard including a channel under the guide plate 102, and a series of locking balls 10% in channel 102a, which leave between each other just so much space that a single stem 69 can enter channel 102 between two balls 102!) whereby each actuated key must return to its normal position of rest before another key can be depressed and actuated. It is also possible to connect a switch, not shown, in series with the voltage divider 94 which is operated by a universal bar, not shown. moved by all stems 69 of all keys K. The switch is of a known type which remains closed for a predetermined time period after its actuation in order to bridge the time elapsing between actuation of the key and response of the circuit even if a key is only very shortly actuated.

It will be seen that the circuit of FIG. 7 according to the invention makes use of capacitor discharge and electroniccomponents to utilize the high operating speed of the electromagnets used as looking and releasing magnet 56, and as stop magnetsMl,M2,M3.

A simplified circuit serving the same purpose and being composed of electromagnetic and nonelectronic circuit components, is shown in FIG. 8 in which components serving the same purpose are indicated by the same reference numerals as in FIG. 7. Contact rings 75a to 75!: are selector contacts 680 to 68h are shown in a developed view. Capacitor 88 is connected in parallel with the locking and releasing magnet 56 to obtain the delay explained above. Holding contacts 72,, 72,, 72 of stop magnets M 1, M 2, M 3 with the single-poleswitch 52, are connected in parallel not only with control contacts 71,, 71,,- 71 but also with .the contacts formed by contact springs 68:; to 68h and the contact rings 75a to 75h.

The type head drive of the invention has been described with reference to a typewriter or like office machine in which the type head is -mounted for tilting movement on the typewriter frame, while a paper sheet is transported with the platen by a paper carriage. Evidently, the arrangement may be reversed in the usual manner, and the type head transported in steps by a carriage along a stationary platen. In such a reverse construction, the above-described circuit components are mounted on the stationary frame of the machine, and the bundle of wires 77 leading to the keyboard code contacts 760 to 76h, and the bundle of wires 87, to 87, are combined in a flexible cable which is dragged by the movable carriage, 'not shown, of the type head means.

Summary I From the above description, it is apparent that the apparatus of the invention comprises drive means M, 10, 100, type head means 17 to 22 and 24 having typefaces 24!, differential transmission means connecting the-drive means with the type head means and including planetary means 13 having a planetary axis 12, control means 48b, 50,56 and 54, 66, M1 to M3 for shifting the differential transmission between a normal condition shown in FIG. 3, and a stop control position in which the planetary'm'eans l3 revolves about the main axis of main shaft 11 and also rotates about the planetary axis ofjournal 12, coupling means 13a, 15, 16a, 16 connecting the plane tary means 13 with the type head means and including a coupling member 13a, 15 secured to the planetary means 13 radially spaced from the planetary axis of journal 12, selector means including keys K and the circuit shown in FIG. 7, and

of an orbit gear 48d.

actuating means 480, 49 for moving the type head means to a printing position when the same substantially stops at the reversing point of the cycloid or cardioid path of coupling member l0.

The differential-transmission means includes main shaft 1], sun gear 14. planetary gear 13, drive gear 9 having journals- 12. The differential transmission means further include a second drive gear 9d mounted on main shaft 11, a second planetary gear'Pmeans' 46, 46a mounted on the second drive gear a, a-second sun gear 45, and acontrol gear in the'form The control means include stop means M -l to M 3, 54, 66, and also locking part 48b, locking pawl :50, and locking and releasing magnet'56;

The actuating meansinclude cam48a connected with gear 48d, and followerroller 49 on the tiltable carrier 21.

A Modified Embodiment FIG. 3a illustrates a modified embodiment which substantially corresponds to the above-described embodiment, and therefore like. parts ,areindicated byreference numerals to which one hundred isadded. Motor gears 110 and 1100 drive drive gears 109 and 109a. Drive gear -.l09 :carries planetary gears 113 and coupling heads 115 in'guideways of a coupling 'f member 116 whichis tiltable with carrier 1 21 about the pivot means 122a so that type head 124 canbe moved from the normal position spaced from the printing;area-t o the printing position.

. Motor gear 110a drives a second drive gear 1090, which carriesa second sun gear 145, whichjis abevel gear, and brackets 150 supporting journals 141- on which secondplanetary gears 1 46 aremounted for rotation aboutan axis trans verse to the main axis of mainshaft 11 1 Abevel sun gear 148 is substituted for the inner gear ring 48d, and is mounted for rotation on the main shaft 111, connected with a locking part i48b which cooperates with a lockingpawl', not shown, while the lower end of shaft 111 carries the stop wheel 154. A cam printing area; differential transmission means connecting said drive means with said type head means and including planetary means having at least one planetary axis spaced from said n'iainaxis; control means for shifting. said differential transmission means between a normal condition in which said planetary means revolves about said main axis without rotating. and a stop control position in which said planetary means revolves about said main axis and also rotates about said planetary'axis; coupling means connecting said planetary means with said type head means and including a coupling member secured to said planetary means radially spaced from said planetary axis so that said type head means is rotated at a constant rotary speed in said normal condition of said differential transmission means to successively placesaid typefaces opposite said printvarying speed and at a minimum speed at said reversing point of said cycloid path; selector means for selecting one of said typefaces for printing, and actuating said control means to shift said differential transmission meansto said stop control position when said planetary means is spacecla predetermined angle from said reversing point and said selected typeface is spaced a predetermined angle fromsaid-position of readiness thereof; and actuating means operated by said differential means at least substantially stops at said reversing point of said cycloid path of said coupling-member, and said selected typeface is in said position of readiness opposite said printing area.

2. An apparatus as claimed in claim 1 wherein said differentialtransmission means includes a main shaft coaxial with said main axis, at least one sun gear secured to said main shaft, said planetary means including atileast one planetary gear meshing with said sun gear and supporting said coupling member; at least one drive gear driven by saiddrive means and having a journal for supporting said planetary gear and mounted on said main shaft for rotation about said axis;

wherein the ratio between said sun gear'and said planetary I gear is l I; wherein in said normalcondition said sun gear rotates at the same speed as said drive gear, and said planetary transmission means so that said planetary gear rolls on said head, a cable '162, andv a follower lever 1'63 cooperating with cam 148b, is provided-for angularly displacing type head 124 between fourpositions in which difierent circular rows of typefaces 12.4! are located opposite the printing area on the platen. I s .j

lt will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of type head driving arrangements differing from the types described above.

While the invention has been illustrated and described as embodied in a type head driving and stopping apparatus in which the type head is stopped at the reversing point of a can I dioid path of a coupling member drivenby a differential transsun gear while revolving aboutsaid main axis so that said ing one reversing point.

3. An apparatus as claimed inf clairn 2 wherein said predetermined angles are both 180,

said type head while said type head'mea'ns is in a normal position spaced from the printing area, said'type head means being 4. An apparatus as claimedin claim- 2 .wherein said control means include stop means for stopping rotation of said main shaft and said sun gear in said normal condition in a predetermined angular position under the. control of said selector means.

5. An apparatuses claimed in claim 4' wherein said-differential transmission means include a second drive gear mounted on said main shaft forrotation about said main axis and being driven by said drive means, second planetary gear means mounted on said second drive gear, a second sun gear fixed to said main shaft and meshing said second planetary gear means,'a control gear concentric with said main axis meshing with said second planetary gearrmeans and being rotatable about said main axis; wherein said actuating means include a cam connected with said control gear for rotation therewith and having a cam portion for actuating said type head means to move from'said normal position to said printing positioni and locking means for locking saidcarn and control gear in said normal condition of said differential transmission means so that said second planetary gear means rotate said second sun gear with said main shaft while rolling on said control gear, and for releasing said control gear in said step coni trol position while said main shaft is stopped by said stop means so that said cam can rotate for actuating said type head means.

6. An apparatus as claimed in claim wherein said drive means rotates said second drive gear at half the rotary speed than the first mentioned drive gear; and wherein said second sun gear rotates at the same rotary speed as said first mentioned drive gear when said control gear is locked.

7. An apparatus as claimed in claim 5 wherein said locking means include a locking part secured to said cam and control gear and having a peripheral cutout, a locking pawl cooperating with said cutout for locking said control gear in one angular position, and a locking and releasing magnet having an ar- 5 mature connected with said locking pawl and a spring biasing said armature and urging said locking pawl to engage said cutout, said locking and releasing magnet retracting said locking pawl, when energized, to release said control gear and cam for rotation; and wherein said selector means include circuit 1 means for energizing said locking and releasing magnet.

8. An apparatus as claimed in claim 7 wherein said control means include a stop wheel secured to said main shaft for rotation therewith and having a series of stop teeth spaced the same angle, a set of stop levers disposed about said stop wheel spaced at a different angle, the number of stop teeth multiplied by the number of stop levers beingequal to the number of said type faces in said circular row, and a-set of stop mag- 5 position.

9. An apparatus as claimed in claim 8 wherein said circuit means include holding contacts for said stop magnets, and a switch connected with said holding contacts and being operated by said locking pawl when the same releases said cutout of said locking part under the control of said locking and releasing magnet, and when the same engages said cutout again after one revolution of said locking part and said cam.

10. An apparatus as claimed in claim 8 wherein said selector means include keys having the same number as said typefaces, and wherein said circuit means include a series or radial contact springs of different length secured to said stop wheel and having the same angular position and number as said series of stop teeth, a support having a circular contact track having the same number of segments as the number of said stop magnets and being slidingly engaged by the outer ends of said contact springs, said support having a series of concentric contact rings respectively slidingly engaged by the inner ends of said radial contact springs, each of said segments being connected with one of said stop magnets, respectively, a series of code contacts having the same number as said locking teeth and being selectively actuated by said keys in accordance with a code, said code contacts beingrespectively connected with said contact rings, means for applying a voltage to said code contacts, a set of control contacts having the same number as said stop magnets and being selectively actuated by said keys,

said control contacts being respectively connected with said stop magnets, and means for applying a voltage to said control contacts whereby a selected stop magnet whose associated control contact is actuated by a key moves the respective stop lever to a stop position located in the path of movement of a predetermined stop tooth for stopping said stop wheel and said main shaft in an angular position in which said selected means include a voltage source, a capacitor charged from said voltage source and connected with said stop magnets and said locking and releasing magnet for energizing the same when discharging, transistor means for controlling the discharge of said capacitor, a flip-flop controllingsaid transistor, voltage divider means connected with said flipflop for switching the same, and a multiple switch connected'with said voltage divider means; and wherein said multiple switch is actuated by said locking pawl when releasing said locking part of said cam means, and again when locking said locking part after one revolution of said cam means in said stop control condition of said differential transmission means.

12. An apparatus as claimed in claim 5' wherein all said gears of said differential transmission means are spur gears, and wherein said control gear is an orbit gear.

13. An apparatus as claimed in claim 5 wherein said second sun gear, said second planetary gear means, and said control gear are bevel gears, said control gear being a sun gear.

14. An apparatus as claimed in claim 1 wherein said type head means includes a type head shaft connected with said type head and having said main axis, and a carrier supporting said type head shaft for rotation; comprising supporting means including pivot means supporting said carrier and thereby said type head means for tilting movement between said normal position and said printing position about an axis transverse to said main axis; wherein said actuating means include a cam follower on said carrier, and cam means rotated by said transmission means about said main axis and having a projecting cam portion for displacing said cam follower and tilting said carrier to said printing position when a selected typeface is in said position of readiness.

15. An apparatus as claimed in claim 1 wherein said type head means include a shaft connected with said type head, a carrier supporting said type head shaft for rotation about said main axis; comprising supporting means including pivot means supporting said carrier and thereby said type head for tilting movement between said normal position and said printing position; wherein said coupling means includes another coupling member secured to said type head shaft and projecting from the same, said other-coupling member having a radial guideway for guiding said first mentioned coupling member which reciprocates along said guideway while moving along said cycloid path, said other coupling member and said guideway moving relative to said first mentioned coupling member during tilting of said carrier.

16. An apparatus as claimed in claim 15 wherein said other coupling member has two radial guideways; wherein said dif ferential transmission means includes a main shaft, and a sun gear secured to said main shaft, wherein said planetary means includes two diametrically disposed planetary gears meshing with said sun gear; wherein said coupling means include two first coupling members having spherical coupling heads respectively guided in said guideways.

17. An apparatus as claimed in claim 1 wherein said selector means include stationary circuit means; wherein said control means include electromagnetic means; a carriage movable in steps along a stationary platen and supporting said type head means, said transmission means, said coupling means, said actuating means and said control means with said electromagnetic means; and cable means connecting said movable carriage with said circuit means of said selector means. 

